I never timed it, since it was designed to be an exhibition piece/sculpture that shows off the mechanism, and not directly tell time. It should be fairly consistent, but each one will be a bit different depending on how it's assembled. Theoretically, you can adjust the number of screws and their depth in the balance wheel to get a nice even BPH of some sort. I'm not sure how well it will work over time though, as the entire sculpture is not perfectly balanced in every point of the 3 axis as it rotates, so it may slow down/speed up as it goes.